Last Monday, Luis's parents gave birth to twins and named them Christopher and Omar. When they were first born, Christopher weighed 6.84 pounds and was 18.5 inches tall, and Omar weighed 7.13 pounds and was 20.5 inches tall. How much did the babies weigh in total?
Explanation: To find the weights of the 2 babies, we need to add their weights together. Christopher's weight + Omar's weight = total weight. ${6}$ ${8}$ ${4}$ ${7}$ ${1}$ ${3}$ ${+\vphantom{0}}$ ${7}$ ${9}$ ${3}$ ${1}$ Together, the babies weigh 13.97 pounds.